Trolling depth control device



Dec. 1, 1970 110L135 3,543,431

TROLLING DEPTH CONTROL DEVICE Filed Feb. 23, 1968 2 Sheets-Sheet 1INVENTOR. PHILIP D. OLDS ATTORNEYS.

Dec. 1, 1970 P. 0.01.05 3,543,431

TROLLING DEPTH CONTROL DEVICE Filed Feb. 23, 1968 2 Sheets-Sheet 2INVENTOR. PHILIP D. OLDS BY ATTORNEYS.

Unitcd States Patent U.S. Cl 43-43.13 6 Claims ABSTRACT OF THEDISCLOSURE Trolling depth control device having a horizontal vane and anupstanding vane, the towing line being attached to the upstanding vaneand the towed line to the horizontal vane, the vanes being of buoyantmaterial but having a lead weight near the front end of the horizontalvane to impart a couple which acts to retain the device beneath thesurface of water in which it is trolled, the couple however beingovercome and reversed if extra drag (for example, due to a fish) isapplied to the towed line, so that the device then moves to the surface.

This invention relates to a depth control device for use in trollingbehind a boat.

Depth control devices have been proposed heretofore and these haveincluded members having weighted forward ends, upstanding vanes andhorizontal vanes, the towing line being secured to an upstanding vanetowards its front end and the towed line being secured to the horizontalvane. (The terms upstanding and horizontal as used herein refer to theapproximate position of vanes when being towed without debris or a fishon the towed line.) With this arrangement the weight ensures that thenormally horizontal vanes will slope downwardly when the towing andtowed lines are horizontal, but will eventually become substantiallyhorizontal when the towing line slopes downwardly to the device.However, the existing type of trolling devices tend to sink, not beingbuoyant, and the depth at which they travel therefore increasesconsiderably as the speed of the towing vessel decreases, and in sinkingthe device tends to become entangled with weed and debris at or near thefloor of the sea.

The main object of this invention is to provide improvements whereby atrolling depth control device will have less tendency to sink butnevertheless will function satisfactorily at retaining a towed linebelow the water surface.

The invention may although not necessarily include as a feature atrolling depth control device having a horizontal vane and an upstandingvane both of buoyant material, the upstanding vane having towing lineattachment means thereon and the horizontal vane having towed lineattachment means thereon.

It will immediately be seen that it is possible to arrange the balanceof buoyancy so that the center of buoyancy is disposed rearwardly of theattachment means for receiving the towing line, and this will thenimpart a moment of couple to the device about an axis normal to thedirection of motion when it first enters the water tending to keep thevertical vane upstanding from the horizontal vane. Once the vane startsmoving through the water it will tend to retain its initial angularposition, that is, with the upstanding vane approximately vertical,owing to the moment of couple imparted by the towing line force and themoment of couple imparted by the towed line force lying in the plane ofthe upstanding vane (for a centrally located towed line).

Two embodiments of the invention are described hereafter in some detailwith reefrence to and are illustrated in the accompanying drawings, inwhich:

3,543,431 Patented Dec. 1, 1970 FIG. 1 shows an equilibrium state of thedevice when being towed (without a fish or debris on the towed line).

FIG. 2 shows an equilibrium state of the device when a fish appliesadditional load to the towed line,

FIG. 3 is an elevation of a depth control device according to a firstembodiment,

FIG. 4 is a plan of FIG. 3,

FIG. 5 is a perspective view showing a second embodiment wherein theupstanding vane can be varied relative to the horizontal vane, and

FIG. 6 is a central elevational section through the device of FIG. 5.

Referring first to the embodiment of FIGS. 3 and 4, a trolling depthcontrol device 10 is provided with what is, for convenience, hereintermed a horizontal vane 11 and an upstanding vane 12 unitary therewith.In this embodiment the material used is polypropylene which has a slightsponge formation so as to be buoyant. The edges of the vanes divergerearwardly to provide a streamlined dart-shaped member capable of movingthrough water without imposing an excessive force to a towing line 13.This is important for sensitivity.

The upstanding vane 12 has a plurality of apertures 15 therein toconstitute towing line attachment means, and the horizontal vane 11 issimilarly provided with apertures 16 to constitute towed line attachmentmeans.

A lead weight 18 is secured to the underside of the nose or leading endof the horizontal vane 11, and is conveniently adjusted for weight sothat the device in its entirety will have approximately the same densityas water, and threfore will not rapidly descend upon variation of speed.

The upper surface 19 of the horizontal vane 11 is of convex shape, andthis assists in directing the nose downwardly for normal towing (FIG. 1)and upwardly when a fish is on the towed line (FIG. 2).

According to the second embodiment of FIGS. 5 and 6, the trolling depthcontrol device 20 again comprises a horizontal vane 11 and an upstandingvane 12. The upstanding vane 1'2, however, is hinged to the horizontalvane about pin 21, near its front end, and screwed near its rear end,the screw 22 passing through a transverse slot 23 in the horizontalplane so that the upstanding vane can be positioned away from center,thus tending to throw the depth control device towards one side or theother of a towing vessel.

The shape of both the horizontal and vertical vanes are again ofstreamlined shape, both vanes being wider near their rear ends than neartheir front ends. As in the first embodiment, the weight 18 is screwedto the underside of the nose of the horizontal vane. The material ofwhich the vanes are made is chosen to be of lower gravity than water, sothat the rear end of the device will tend to float and so that thebuoyancy center of the device is towards its rear end.

Forwardly of the buoyancy center of the device is disposed the pluralityof apertures 15 through the vertical vane near its upper edge, theseapertures being arranged to receive a towing line, while the apertures16 in the horizontal vane 11 near its rear end are arranged to receive atowed line. The towing line attachment apertures 15 are a short distanceabove the towed line attachment apertures 16 but disposed forwardlythereof by a much greater distance. Under normal towing conditionstherefor the towing line is nearly horizontal, having but a small upwardslope, while the towed line is substantially horizontal. The resultantupward force is relatively small. However, the towed line apertures 16,in normally being lower than the towing line apertures 15, cause thevane 11 to adjust its position and the front end of the lure to dipdownwardly. This causes a downward force on the vane 11 which will equalthe resultant upward force for a stable tow condition. If moments ofcouple are considered about the towing point of the towing line, theweight on the nose multiplied by its distance forwardly of the towingpoint will cause an anticlockwise moment which is equalled by clockwisemoment due to the downward force on the downwardly sloping vane 11multiplied by the distance of its effective point of applicationrearwardly of the towing point. The device will resist any tendency torotate over on its back so that it would then shoot to the surface,since such rotation would result in drawing the towed line forwardly andwould lift the weight 18 up to a position similar to that shown in FIG.2. However, when the additional loading of a fish, or debris on thetowed line is transmitted to the device, the device will then have itsequilibrium of forces upset, the force and moment arm dimension due todrag of the towed-line both being increased, while at the same time theangle of dip is decreased. This provides an unstable set of conditionscorrected only by inversion of the device which results in its moving tothe surface (FIG. 2).

This invention, though simple, provides a device which is effective inretaining a towed line at the desired depth but is sensitive tovariation in drag of the towed line. It will be seen that since thedevice is little if any denser than water, it dose not tend to sink whenway is lost, so that it will not so readily foul debris or weed at thefloor of the sea or river in which it is to be used. Furthermore, itwill be appreciated that the device is comprised of very low costportions and therefore is cheaper than previously proposed devices.Furthermore, it will be seen that since the weight of the device issmall, it is more responsive to changes of loading in the towed line,for example, due to a fish biting, and is therefore of more use to asportsman.

What I claim is:

1. A trolling depth control device having a horizontal vane and anupstanding vane both of buoyant material, the edges of the horizontalvane diverging in a rearward direction, a weight on the underside of thehorizontal vane near its front end, the upper edge of the upstandingvane diverging away from the horizontal vane in a rearward direction, aseries of apertures through the upstanding vane near its upper edge, anda series of apertures through the horizontal vane near its rear end, thetowing line attachment means being a short distance above the towed lineattachment but a much greater distance forwardly of the towed lineattachment means whereby moments of couple during towing are equal ifthe horizontal vane slopes downwardly towards its nose, but uponincrease of loading on the towed line the moments of couple rotate thedevice to direct its nose upwardly.

2. A trolling depth control device as in claim 1 where said series ofapertures through the upstanding vane are the towing line attachmentmeans and said series of apertures through the horizontal vanes are thetowed line attachment means, and said weight is positioned forwardly ofsaid towing line attachment means.

3. A trolling depth control device as in claim 1 where said horizontalvane has an upper surface, in a no-extraload condition, of convex shape.

4. A trolling depth control device having a horizontal vane and anupstanding vane both of buoyant material, a weight on the underside ofthe horizontal vane near its front end, towing line attachment means onthe upstanding vane, and towed line attachment means on the horizontalvane, the towing line attachment means being a short distance above thetowed line attachment means but a much greater distance forwardly of thetowed line attachment means whereby moments of couple about the towingpoint during towing are equal only if the horizontal vane slopesdownwardly towards its nose, the effective said moments then being, inone direction, said weight multiplied by its distance forwardly of thetowing point, and in the other direction, the downward force on thehorizontal vane due to its passage through the water multiplied by itseffective distance rearwardly of the towing point, but upon increase ofloading on the towed line the moments of couple rotate the device todirect its nose upwardly.

5. A trolling depth control device according to claim 4 wherein thevanes are constituted by a unitary moulded member of resin-basedthermoplastics material.

6. A trolling depth control device according to claim 4 wherein theupstanding vane is pivoted about a vertical axis to the horizontal vanethereby being adjustable relative thereto, and securing means betweenthe vanes are operable to fix them relatively to one another in any oneof a plurality of adjustable positions.

References Cited UNITED STATES PATENTS 1,875,122 8/1932 Olson 4342.52,731,755 1/1956 Ward et al 4343.13 2,924,907 2/ 1960 Hamilton 43-43132,940,207 6/1960 Scott 4343.13 3,032,912 5/1962 Bengtsson 43-43.133,135,065 6/1964 Cromoga 43--43.13 2,798,331 7/1957 Westdahl 43-43.13

SAMUEL KOREN, Primary Examiner D. J. LEACH, Assistant Examiner

